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Fix #15092: False positive: uninitvar with Microsoft CRT localtime_s. #8924

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Fix #15092: False positive: uninitvar with Microsoft CRT localtime_s. #8924

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f743809
update tests
ludviggunne Oct 7, 2026
5426ee6
add test
ludviggunne Oct 7, 2026
f5f75fb
fix
ludviggunne Oct 7, 2026
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11 changes: 5 additions & 6 deletions cfg/std.cfg
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Original file line number Diff line number Diff line change
Expand Up @@ -3238,16 +3238,15 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
<not-uninit/>
</arg>
</function>
<!-- struct tm *localtime_s(const time_t *restrict time, struct tm *restrict result) -->
<function name="localtime_s,std::localtime_s">
<returnValue type="struct tm *"/>
<!-- struct tm *localtime_s(const time_t *restrict time, struct tm *restrict result)

@chrchr-github chrchr-github Oct 7, 2026

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Apparently gmtime_s() has the same issue, see https://trac.cppcheck.net/ticket/11826

Order of arguments and return type differs between implementations, define a common baseline here. -->
<function name="localtime_s">
<noreturn>false</noreturn>
<leak-ignore/>
<arg nr="1" direction="in">
<arg nr="1">
<not-null/>
<not-uninit/>
</arg>
<arg nr="2" direction="out">
<arg nr="2">
<not-null/>
</arg>
</function>
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5 changes: 3 additions & 2 deletions cfg/windows.cfg
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Expand Up @@ -4654,9 +4654,10 @@ HFONT CreateFont(
<not-uninit/>
</arg>
</function>
<!-- errno_t _localtime32_s( struct tm* _tm, const __time32_t *time);
<!-- errno_t localtime_s( struct tm* const tmDest, time_t const* const sourceTime);
errno_t _localtime32_s( struct tm* _tm, const __time32_t *time);
errno_t _localtime64_s( struct tm* _tm, const __time64_t *time); -->
<function name="_localtime32_s,_localtime64_s">
<function name="localtime_s,_localtime32_s,_localtime64_s">
<returnValue type="errno_t"/>
<noreturn>false</noreturn>
<leak-ignore/>
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20 changes: 0 additions & 20 deletions test/cfg/std.c
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Expand Up @@ -171,26 +171,6 @@ void nullPointer_qsort(void *base, size_t n, size_t size, int (*cmp)(const void
qsort(base, n, size, qsort_cmpfunc);
}

// As with all bounds-checked functions, localtime_s is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including time.h.
#ifdef __STDC_LIB_EXT1__
void uninitvar_localtime_s(const time_t *restrict time, struct tm *restrict result)
{
const time_t *restrict Time;
// cppcheck-suppress uninitvar
(void)localtime_s(Time, result);
(void)localtime_s(time, result);
}

void nullPointer_localtime_s(const time_t *restrict time, struct tm *restrict result)
{
// cppcheck-suppress nullPointer
(void)localtime_s(NULL, result);
// cppcheck-suppress nullPointer
(void)localtime_s(time, NULL);
(void)localtime_s(time, result);
}
#endif // __STDC_LIB_EXT1__

size_t bufferAccessOutOfBounds_wcsrtombs(char * dest, const wchar_t ** src, size_t len, mbstate_t * ps)
{
char buf[42];
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32 changes: 0 additions & 32 deletions test/cfg/std.cpp
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Expand Up @@ -689,38 +689,6 @@ void *bufferAccessOutOfBounds_memchr(void *s, int c, size_t n)
return std::memchr(s,c,n);
}

// As with all bounds-checked functions, localtime_s is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including time.h.
#ifdef __STDC_LIB_EXT1__
void uninitvar_localtime_s(const std::time_t *restrict time, struct tm *restrict result)
{
// cppcheck-suppress valueFlowBailoutIncompleteVar
const std::time_t *restrict Time;
// TODO cppcheck-suppress uninitvar
(void)std::localtime_s(Time, result);
(void)std::localtime_s(time, result);
}

void nullPointer_localtime_s(const std::time_t *restrict time, struct tm *restrict result)
{
// cppcheck-suppress nullPointer
(void)std::localtime_s(NULL, result);
// cppcheck-suppress nullPointer
(void)std::localtime_s(time, NULL);
(void)std::localtime_s(time, result);
}

void memleak_localtime_s(const std::time_t *restrict time, struct tm *restrict result) // #9258
{
const time_t t = time(0);
const struct tm* const now = new tm();
if (localtime_s(now, &t) == 0) {
// cppcheck-suppress valueFlowBailoutIncompleteVar
std::cout << now->tm_mday << std::endl;
}
// cppcheck-suppress memleak
}
#endif // __STDC_LIB_EXT1__

size_t nullPointer_strftime(char *s, size_t max, const char *fmt, const struct tm *p)
{
// cppcheck-suppress nullPointer
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28 changes: 28 additions & 0 deletions test/cfg/windows.cpp
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Expand Up @@ -1260,3 +1260,31 @@ void constParameterPointer_SetupDiGetDeviceInstanceId(HDEVINFO info, SP_DEVINFO_
TCHAR buffer[buffer_size];
SetupDiGetDeviceInstanceId(info, data, buffer, buffer_size, NULL);
}

void uninitvar_localtime_s(const time_t *time, struct tm *result)
{
time_t uninit_time;
struct tm uninit_result;
// cppcheck-suppress uninitvar
(void)localtime_s(result, &uninit_time);
(void)localtime_s(&uninit_result, time);
(void)localtime_s(result, time);
}

void nullPointer_localtime_s(const time_t *time, struct tm *result)
{
// cppcheck-suppress nullPointer
(void)localtime_s(result, NULL);
// cppcheck-suppress nullPointer
(void)localtime_s(NULL, time);
(void)localtime_s(result, time);
}

void memleak_localtime_s(void) // #9258
{
const time_t t = time(0);
struct tm *const now = new tm();
if (localtime_s(now, &t) == 0)
printf("%d\n", now->tm_mday);
// cppcheck-suppress memleak
}
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